An example of conventional thermal print head is shown in FIGS. 7 and 8. As shown in FIG. 7, a conventional thermal print head 101 includes an insulating board 102, a heating resistor 103, and a drive IC 104. The board 102 is provided with a connector 105 for connecting to an external device.
As shown in FIG. 8, the surface of the board 102 is provided with a glaze layer 121. The upper surface of the glaze layer 121 is provided with a predetermined wiring pattern 122. The wiring pattern 122 is partly provided with conductive pads 161 which serve as electrodes. The connector 105 is provided with a plurality of pins 151, and each pin 151 includes an engaging portion 151a for clamping the board 102. When the connector 105 is attached to the board 102, each pin 151 contacts a corresponding electrode 161. For preventing dropout of the connector 105 from the board 102, resin 107 is provided to partially cover the pin 151 at the upper and lower surfaces of the board 102.
Due to the above-described structure, the resin 107 can keep the pin 151 and the electrode 161 in contacting manner. However, for example, if heat is applied on the resin 107 when the print head is driven, the resin 107 is softened so that the pin 151 may be detached from the electrode 161.
The above-described problem can be solved by soldering the pin to the electrode. An example of such arrangement is disclosed in JP-A-07-30218. Specifically, as shown in FIG. 4 of the above application, a pin (24) is soldered to an electrode (15) on a glaze layer (12), and then partially covered by a protecting resin (21). With such an arrangement, even if the protecting resin is softened due to heat, the pin and the electrode can keep their jointed manner.
However, soldering causes following disadvantage. Solder tends to contract when solidified. Thus, when the pin is soldered to the electrode, as the solder contracts, the electrode may be detached from the glaze layer or the glaze layer may be damaged.